Image projection apparatus

1. An image projection apparatus comprising: a reflective display device that has pixels and that displays an image through angle modulation of the pixels; a light source that emits illumination light for illuminating the display device; an illumination optical system that directs the illumination light from the light source to the display device; and a projection optical system that has four curved-surface mirrors and that projects, as image light, light representing the image from the display device, wherein a deflection axis of the pixels is parallel to longer sides of a rectangular display area of the display device, wherein a center of an entrance pupil of the projection optical system is located at a position displaced from a line normal to a center of the display area in a direction parallel to shorter sides of the display area, wherein a center of an exit pupil of the illumination optical system is located at a position displaced from the line normal to the center of the display area in the direction parallel to the shorter sides of the display area but opposite to the direction in which the center of the entrance pupil of the projection optical system is displaced from the line normal to the center of the display area, wherein the illumination optical system is so arranged that the image light from the display device passes through the entrance pupil of the projection optical system, and wherein the projection optical system has a lens between a first mirror and a second mirror as counted from a display device side thereof.

2. The image projection apparatus of claim 1 , wherein conditional formulae (i) and (ii) below are fulfilled: L · { tan ⁢ [ tan - 1 ⁡ ( tan ⁢ ⁢ α + d 2 · H ) - θ ] + tan ⁢ [ tan - 1 ⁡ ( tan ⁢ ⁢ α - d 2 · H ) - θ + 2 · χ ] } > d ( i ) sin ⁢ ⁢ θ > 0.13 ( ii ) where, let a reference direction be a direction of a line normal to the display area of the display device, L represents a distance, in the reference direction, from the display area of the display device to an optical component located closest to the display area of the display device on an optical path; α represents an angle, to the reference direction, of a direction pointing from the center of the display area of the display device to the center of the entrance pupil of the projection optical system; d represents a length of the shorter sides of the display area of the display device; H represents a distance, in the reference direction, from the display area of the display device to the entrance pupil of the projection optical system; θ represents an arcsine of a numerical aperture of the illumination optical system and the projection optical system as measured in a direction parallel to the shorter sides of the display area of the display device; and χ represents a deflection angle at which the pixels are deflected relative to a display surface of the display device.

3. The image projection apparatus of claim 2 , wherein the illumination optical system comprises an integrator optical system that illuminates an area including the display area of the display device and is geometrically substantially similar to the display area of the display device.

7. The image projection apparatus of claim 1 , wherein the display device is a digital micromirror device.